fix(text): fix panic when rendering out of bounds (#997)

Previously it was possible to cause a panic when rendering to an area
outside of the buffer bounds. Instead this now correctly renders nothing
to the buffer.

src/text/line.rs

@@ -587,6 +587,11 @@ mod tests {
 
     use super::*;
 
+    #[fixture]
+    fn small_buf() -> Buffer {
+        Buffer::empty(Rect::new(0, 0, 10, 1))
+    }
+
     #[test]
     fn raw_str() {
         let line = Line::raw("test content");
@@ -832,6 +837,7 @@ mod tests {
         const GREEN: Style = Style::new().fg(Color::Green);
         const ITALIC: Style = Style::new().add_modifier(Modifier::ITALIC);
 
+        #[fixture]
         fn hello_world() -> Line<'static> {
             Line::from(vec![
                 Span::styled("Hello ", BLUE),
@@ -851,6 +857,13 @@ mod tests {
             assert_buffer_eq!(buf, expected);
         }
 
+        #[rstest]
+        fn render_out_of_bounds(hello_world: Line<'static>, mut small_buf: Buffer) {
+            let out_of_bounds = Rect::new(20, 20, 10, 1);
+            hello_world.render(out_of_bounds, &mut small_buf);
+            assert_buffer_eq!(small_buf, Buffer::empty(small_buf.area));
+        }
+
         #[test]
         fn render_only_styles_line_area() {
             let mut buf = Buffer::empty(Rect::new(0, 0, 20, 1));

src/text/span.rs

@@ -363,6 +363,7 @@ impl Widget for Span<'_> {
 
 impl WidgetRef for Span<'_> {
     fn render_ref(&self, area: Rect, buf: &mut Buffer) {
+        let area = area.intersection(buf.area);
         let Rect {
             x: mut current_x,
             y,
@@ -402,8 +403,15 @@ impl std::fmt::Display for Span<'_> {
 
 #[cfg(test)]
 mod tests {
+    use rstest::fixture;
+
     use super::*;
 
+    #[fixture]
+    fn small_buf() -> Buffer {
+        Buffer::empty(Rect::new(0, 0, 10, 1))
+    }
+
     #[test]
     fn default() {
         let span = Span::default();
@@ -533,6 +541,8 @@ mod tests {
     }
 
     mod widget {
+        use rstest::rstest;
+
         use super::*;
         use crate::assert_buffer_eq;
 
@@ -550,6 +560,13 @@ mod tests {
             assert_buffer_eq!(buf, expected);
         }
 
+        #[rstest]
+        fn render_out_of_bounds(mut small_buf: Buffer) {
+            let out_of_bounds = Rect::new(20, 20, 10, 1);
+            Span::raw("Hello, World!").render(out_of_bounds, &mut small_buf);
+            assert_eq!(small_buf, Buffer::empty(small_buf.area));
+        }
+
         /// When the content of the span is longer than the area passed to render, the content
         /// should be truncated
         #[test]

src/text/text.rs

@@ -559,6 +559,7 @@ impl Widget for Text<'_> {
 
 impl WidgetRef for Text<'_> {
     fn render_ref(&self, area: Rect, buf: &mut Buffer) {
+        let area = area.intersection(buf.area);
         buf.set_style(area, self.style);
         for (line, row) in self.iter().zip(area.rows()) {
             let line_width = line.width() as u16;
@@ -601,6 +602,11 @@ mod tests {
 
     use super::*;
 
+    #[fixture]
+    fn small_buf() -> Buffer {
+        Buffer::empty(Rect::new(0, 0, 10, 1))
+    }
+
     #[test]
     fn raw() {
         let text = Text::raw("The first line\nThe second line");
@@ -865,6 +871,13 @@ mod tests {
             assert_buffer_eq!(buf, expected_buf);
         }
 
+        #[rstest]
+        fn render_out_of_bounds(mut small_buf: Buffer) {
+            let out_of_bounds_area = Rect::new(20, 20, 10, 1);
+            Text::from("Hello, world!").render(out_of_bounds_area, &mut small_buf);
+            assert_eq!(small_buf, Buffer::empty(small_buf.area));
+        }
+
         #[test]
         fn render_right_aligned() {
             let text = Text::from("foo").alignment(Alignment::Right);